1. Field of the Invention
The present invention relates to an optical disc apparatus that reads information from or writes information to an optical disc.
2. Description of Related Art
Today, optical discs such as CDs (compact discs) and DVDs (digital versatile discs) are widely used as media for recording video, audio, or information. These optical discs are used as recording media on optical disc apparatuses, which record data to an optical disc by irradiating a recording surface thereof with laser light emitted from an optical head and (or) reads data from the optical disc by detecting the light reflected from the recording surface.
In common optical disc apparatuses, an optical disc is placed on a tray (disc tray), and this tray is, by a drive force transmitted thereto from a drive motor, moved back (loaded) into and moved forth (unloaded) out of an exterior housing through a slit-like opening formed in the front panel thereof.
Such an optical disc apparatus includes a main chassis unit, a traverse chassis that is fitted to the main chassis unit so as to be rotatable, and an optical head that is fitted to the traverse chassis so as to be linearly slidable on a reciprocating fashion. The traverse chassis is provided with an optical disc driving mechanism that clamps the optical disc and makes it rotate. As the traverse chassis is moved up and down, the optical disc driving mechanism clamps and unclamps the optical disc placed on the disc tray. As the optical head slides, varying parts of the clamped optical disc, between the inner and outer edges thereof, are irradiated with laser light.
In common optical disc apparatuses, the drive force for loading/unloading the disc tray, the drive force for moving up and down the traverse chassis, and the drive force for making the optical head slide are all supplied from a single drive motor while the destination to which to transmit its drive force is switched with proper timing.
For example, unloading is achieved in the following manner. First the optical head is moved to the inner edge of the optical disc. Then the traverse chassis is moved down so that none of the components (such as the optical head) provided thereon interferes with the unloading of the disc tray. Now the disc tray is moved forth so as to be unloaded.
In the inventions disclosed in JP-A-2005-174427 and JP-A-2004-253130, the switching of the destination of the drive force is achieved by use of a cam slider and a trigger plate. When the optical pickup (optical head) is moved to the inner edge of the optical disc, the trigger plate slides. As the trigger plate moves, it pushes the cam slider and makes it move together. The cam slider is provided with a rack, which then meshes with a gear that transmits the drive force, so that the drive force is now transmitted to the cam slider.
As the cam slider moves, the traverse chassis, which is engaged with the cam slider in a cam groove formed therein, moves down, and the disc tray, which is engaged with the cam slider at another place thereon, also moves. The disc tray is provided with a rack, and thus moves together with the cam slider. Now the rack meshes with a gear and the disc tray is unloaded.
At this point, a boss formed on a slider rack of the optical pickup is engaged with the trigger plate, and thereby restricts the movement of the optical pickup. Loading is achieved through a reversed sequence of the actions described above.
To realize the above-mentioned three kinds of movement with a single motor, the drive motor is fitted to the traverse chassis, and its shaft is fitted with a worm gear.
Inconveniently, however, this conventional construction has the following disadvantages. Since the trigger plate is fitted to the traverse chassis, the trigger plate may occasionally move together with the traverse chassis. Simultaneous movement of the trigger plate and the traverse chassis is likely to produce errors in the timing of the movement of the optical pickup and the cam slider, and therefore it is necessary to prevent the movement of the traverse chassis from hampering the movement of the trigger plate. This accordingly diminishes the flexibility in the design of the traverse chassis, the optical pickup, and the cam slider.
Moreover, the trigger plate does not receive the drive force but simply follows the movement of the optical pickup and (or) the cam slider. This imposes a burden on the movement of the optical pickup and (or) the cam slider, and may lead to lower movement accuracy. Moreover, parts of the optical pickup and the cam slider need to be so formed as to engage with the trigger plate, and need to be given sufficient mechanical strength. This requires extra trouble and time in production.
Furthermore, providing the trigger plate increases the number of components of an optical disc apparatus, and also increases the trouble and time required in assembly, leading to accordingly higher costs in production and assembly.